This invention relates to a system for magnetic suspension of objects. More specifically, it relates to a system that enables an object to float at a certain position unsupported by any mechanical attachment. The position of the floating object is closely controlled by a microprocessor controlled electromagnetic source.
In the past, magnetism has been used to float objects with varying degrees of limitations. For example, PCT Application No. WO 97/09540 discloses a system for magnetically suspending an object. The system employs a strong permanent magnet in the object being floated and a separate solenoid, comprised of a large coil wrapped around a small permanent magnet and two small cylindrical soft iron core pieces. In addition, two Hall effect sensors are provided to sense field intensity at the end of the coil assembly, and an electronic circuit converts the sensors"" output to control the coil current. The principle force offsetting gravity of the object being floated is the attraction of the permanent magnet.
To operate this system, a user must adjust one or two potentiometers that translate the amplified sensor signals to a voltage range accepted by a set of voltage comparators. When adjusted correctly for the weight of the object to be floated, a relatively small current in the coil will cause a force that acts to repel the permanent magnet in the floating object to achieve a balance such that the total magnetic field applied cancels out the gravity. Once the object is in this balanced position, any deviation in the position of the floating object in the magnetic field produces a change in the Hall effect sensor""s output which results in an imbalance in the comparator circuit. The comparator signals are then converted to pulse width modulated (xe2x80x9cPWMxe2x80x9d) signals of correct polarity to change the coil current signal and hence adjust the overall magnetic field in such a way as to push the object back to the position of balance.
This prior system encounters several problems. For example, because the system amplifies the Hall effect sensor output by a factor of 8-10 thousand, a weight change of only a few ounces of the floating object will cause a change in position that will in turn drive the amplified signal out of the useful range of the comparators. As a result, non-technically proficient users of the system (such as sales and marketing people who may need to float a variety of objects) must become proficient in making rather complicated and sensitive adjustments. Such a requirement is undesirable.
Also, the system requires that the coil assembly be mechanically isolated from its mounting structure because it is not always possible to hold the floating object when the system is mechanically perturbed, e.g., bumped or vibrated. The coil assembly is therefore hung from its mounting position by an elastic band which reduces the effect of a mechanical input. However, using such a band causes certain mechanical problems; for example, the coil assembly must be allowed to droop below its mounting structure which makes the packaging less attractive and adds to the overall size of the system. The band also greatly complicates assembly of the system.
An improved method and system is needed for easily and smoothly placing a floating object in a balanced position and thereafter for continuously and automatically controlling the position of the floating object, and for avoiding disruptions caused by minor external forces perturbing the floating object. An improved, more economical circuit design for such a system is also needed. In addition, an improved method and system is needed to accommodate suspension of a wide weight range of objects.
The present invention provides an improved and economical system and method for magnetically floating an object. The system provides a user friendly interface for initially placing the object to be floated in a proximately balanced position. The system swiftly adjusts the object to a position such that a stable, floating condition is met. Once the object is located in the stable position, the system continuously, automatically, and intelligently adjusts the position of the floating object, responding to minor position changes of the object to keep the object floating without disruption. A wide weight range of objects can be accommodated for flotation.
The system includes an improved electromagnetic source that is relatively precise in the support of objects, while reducing the overall cost of the system. A control circuit of the electromagnetic source utilizes a microprocessor and a single Hall effect sensor. The Hall sensor""s output voltage passes through an amplifier and is moderately amplified, e.g., by a factor of about 10, and is then sent to an analog to digital conversion input of the microprocessor. Signals are processed in the microprocessor, and the resulting output signals are directed to a current generating circuit for continuously controlling and adjusting the position of the floating object by modifying characteristics of a magnetic field created by the electromagnetic source.